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/*
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 * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos
 *
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
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 *  * Redistributions of source code must retain the above copyright notice,
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package java.time.chrono;

import static java.time.chrono.JapaneseDate.MEIJI_6_ISODATE;
import static java.time.temporal.ChronoField.ERA;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.io.InvalidObjectException;
import java.io.ObjectInputStream;
import java.io.ObjectStreamException;
import java.io.Serializable;
import java.time.DateTimeException;
import java.time.LocalDate;
import java.time.temporal.ChronoField;
import java.time.temporal.TemporalField;
import java.time.temporal.UnsupportedTemporalTypeException;
import java.time.temporal.ValueRange;
import java.util.Arrays;
import java.util.Objects;

import sun.util.calendar.CalendarDate;

/**
 * An era in the Japanese Imperial calendar system.
 * <p>
 * This class defines the valid eras for the Japanese chronology.
 * Japan introduced the Gregorian calendar starting with Meiji 6.
 * Only Meiji and later eras are supported;
 * dates before Meiji 6, January 1 are not supported.
 *
 * @implSpec This class is immutable and thread-safe.
 * @since 1.8
 */
public final class JapaneseEra
    implements Era, Serializable {

  // The offset value to 0-based index from the era value.
  // i.e., getValue() + ERA_OFFSET == 0-based index
  static final int ERA_OFFSET = 2;

  static final sun.util.calendar.Era[] ERA_CONFIG;

  /**
   * The singleton instance for the 'Meiji' era (1868-01-01 - 1912-07-29)
   * which has the value -1.
   */
  public static final JapaneseEra MEIJI = new JapaneseEra(-1, LocalDate.of(1868, 1, 1));
  /**
   * The singleton instance for the 'Taisho' era (1912-07-30 - 1926-12-24)
   * which has the value 0.
   */
  public static final JapaneseEra TAISHO = new JapaneseEra(0, LocalDate.of(1912, 7, 30));
  /**
   * The singleton instance for the 'Showa' era (1926-12-25 - 1989-01-07)
   * which has the value 1.
   */
  public static final JapaneseEra SHOWA = new JapaneseEra(1, LocalDate.of(1926, 12, 25));
  /**
   * The singleton instance for the 'Heisei' era (1989-01-08 - current)
   * which has the value 2.
   */
  public static final JapaneseEra HEISEI = new JapaneseEra(2, LocalDate.of(1989, 1, 8));

  // the number of defined JapaneseEra constants.
  // There could be an extra era defined in its configuration.
  private static final int N_ERA_CONSTANTS = HEISEI.getValue() + ERA_OFFSET;

  /**
   * Serialization version.
   */
  private static final long serialVersionUID = 1466499369062886794L;

  // array for the singleton JapaneseEra instances
  private static final JapaneseEra[] KNOWN_ERAS;

  static {
    ERA_CONFIG = JapaneseChronology.JCAL.getEras();

    KNOWN_ERAS = new JapaneseEra[ERA_CONFIG.length];
    KNOWN_ERAS[0] = MEIJI;
    KNOWN_ERAS[1] = TAISHO;
    KNOWN_ERAS[2] = SHOWA;
    KNOWN_ERAS[3] = HEISEI;
    for (int i = N_ERA_CONSTANTS; i < ERA_CONFIG.length; i++) {
      CalendarDate date = ERA_CONFIG[i].getSinceDate();
      LocalDate isoDate = LocalDate.of(date.getYear(), date.getMonth(), date.getDayOfMonth());
      KNOWN_ERAS[i] = new JapaneseEra(i - ERA_OFFSET + 1, isoDate);
    }
  }

  ;

  /**
   * The era value.
   *
   * @serial
   */
  private final transient int eraValue;

  // the first day of the era
  private final transient LocalDate since;

  /**
   * Creates an instance.
   *
   * @param eraValue the era value, validated
   * @param since the date representing the first date of the era, validated not null
   */
  private JapaneseEra(int eraValue, LocalDate since) {
    this.eraValue = eraValue;
    this.since = since;
  }

  //-----------------------------------------------------------------------

  /**
   * Returns the Sun private Era instance corresponding to this {@code JapaneseEra}.
   *
   * @return the Sun private Era instance for this {@code JapaneseEra}.
   */
  sun.util.calendar.Era getPrivateEra() {
    return ERA_CONFIG[ordinal(eraValue)];
  }

  //-----------------------------------------------------------------------

  /**
   * Obtains an instance of {@code JapaneseEra} from an {@code int} value.
   * <p>
   * The {@link #SHOWA} era that contains 1970-01-01 (ISO calendar system) has the value 1
   * Later era is numbered 2 ({@link #HEISEI}). Earlier eras are numbered 0 ({@link #TAISHO}),
   * -1 ({@link #MEIJI}), only Meiji and later eras are supported.
   *
   * @param japaneseEra the era to represent
   * @return the {@code JapaneseEra} singleton, not null
   * @throws DateTimeException if the value is invalid
   */
  public static JapaneseEra of(int japaneseEra) {
    if (japaneseEra < MEIJI.eraValue || japaneseEra + ERA_OFFSET > KNOWN_ERAS.length) {
      throw new DateTimeException("Invalid era: " + japaneseEra);
    }
    return KNOWN_ERAS[ordinal(japaneseEra)];
  }

  /**
   * Returns the {@code JapaneseEra} with the name.
   * <p>
   * The string must match exactly the name of the era.
   * (Extraneous whitespace characters are not permitted.)
   *
   * @param japaneseEra the japaneseEra name; non-null
   * @return the {@code JapaneseEra} singleton, never null
   * @throws IllegalArgumentException if there is not JapaneseEra with the specified name
   */
  public static JapaneseEra valueOf(String japaneseEra) {
    Objects.requireNonNull(japaneseEra, "japaneseEra");
    for (JapaneseEra era : KNOWN_ERAS) {
      if (era.getName().equals(japaneseEra)) {
        return era;
      }
    }
    throw new IllegalArgumentException("japaneseEra is invalid");
  }

  /**
   * Returns an array of JapaneseEras.
   * <p>
   * This method may be used to iterate over the JapaneseEras as follows:
   * <pre>
   * for (JapaneseEra c : JapaneseEra.values())
   *     System.out.println(c);
   * </pre>
   *
   * @return an array of JapaneseEras
   */
  public static JapaneseEra[] values() {
    return Arrays.copyOf(KNOWN_ERAS, KNOWN_ERAS.length);
  }

  //-----------------------------------------------------------------------

  /**
   * Obtains an instance of {@code JapaneseEra} from a date.
   *
   * @param date the date, not null
   * @return the Era singleton, never null
   */
  static JapaneseEra from(LocalDate date) {
    if (date.isBefore(MEIJI_6_ISODATE)) {
      throw new DateTimeException("JapaneseDate before Meiji 6 are not supported");
    }
    for (int i = KNOWN_ERAS.length - 1; i > 0; i--) {
      JapaneseEra era = KNOWN_ERAS[i];
      if (date.compareTo(era.since) >= 0) {
        return era;
      }
    }
    return null;
  }

  static JapaneseEra toJapaneseEra(sun.util.calendar.Era privateEra) {
    for (int i = ERA_CONFIG.length - 1; i >= 0; i--) {
      if (ERA_CONFIG[i].equals(privateEra)) {
        return KNOWN_ERAS[i];
      }
    }
    return null;
  }

  static sun.util.calendar.Era privateEraFrom(LocalDate isoDate) {
    for (int i = KNOWN_ERAS.length - 1; i > 0; i--) {
      JapaneseEra era = KNOWN_ERAS[i];
      if (isoDate.compareTo(era.since) >= 0) {
        return ERA_CONFIG[i];
      }
    }
    return null;
  }

  /**
   * Returns the index into the arrays from the Era value.
   * the eraValue is a valid Era number, -1..2.
   *
   * @param eraValue the era value to convert to the index
   * @return the index of the current Era
   */
  private static int ordinal(int eraValue) {
    return eraValue + ERA_OFFSET - 1;
  }

  //-----------------------------------------------------------------------

  /**
   * Gets the numeric era {@code int} value.
   * <p>
   * The {@link #SHOWA} era that contains 1970-01-01 (ISO calendar system) has the value 1.
   * Later eras are numbered from 2 ({@link #HEISEI}).
   * Earlier eras are numbered 0 ({@link #TAISHO}), -1 ({@link #MEIJI})).
   *
   * @return the era value
   */
  @Override
  public int getValue() {
    return eraValue;
  }

  //-----------------------------------------------------------------------

  /**
   * Gets the range of valid values for the specified field.
   * <p>
   * The range object expresses the minimum and maximum valid values for a field.
   * This era is used to enhance the accuracy of the returned range.
   * If it is not possible to return the range, because the field is not supported
   * or for some other reason, an exception is thrown.
   * <p>
   * If the field is a {@link ChronoField} then the query is implemented here.
   * The {@code ERA} field returns the range.
   * All other {@code ChronoField} instances will throw an {@code UnsupportedTemporalTypeException}.
   * <p>
   * If the field is not a {@code ChronoField}, then the result of this method
   * is obtained by invoking {@code TemporalField.rangeRefinedBy(TemporalAccessor)}
   * passing {@code this} as the argument.
   * Whether the range can be obtained is determined by the field.
   * <p>
   * The range of valid Japanese eras can change over time due to the nature
   * of the Japanese calendar system.
   *
   * @param field the field to query the range for, not null
   * @return the range of valid values for the field, not null
   * @throws DateTimeException if the range for the field cannot be obtained
   * @throws UnsupportedTemporalTypeException if the unit is not supported
   */
  @Override  // override as super would return range from 0 to 1
  public ValueRange range(TemporalField field) {
    if (field == ERA) {
      return JapaneseChronology.INSTANCE.range(ERA);
    }
    return Era.super.range(field);
  }

  //-----------------------------------------------------------------------
  String getAbbreviation() {
    int index = ordinal(getValue());
    if (index == 0) {
      return "";
    }
    return ERA_CONFIG[index].getAbbreviation();
  }

  String getName() {
    return ERA_CONFIG[ordinal(getValue())].getName();
  }

  @Override
  public String toString() {
    return getName();
  }

  //-----------------------------------------------------------------------

  /**
   * Defend against malicious streams.
   *
   * @param s the stream to read
   * @throws InvalidObjectException always
   */
  private void readObject(ObjectInputStream s) throws InvalidObjectException {
    throw new InvalidObjectException("Deserialization via serialization delegate");
  }

  //-----------------------------------------------------------------------

  /**
   * Writes the object using a
   * <a href="../../../serialized-form.html#java.time.chrono.Ser">dedicated serialized form</a>.
   *
   * @return the instance of {@code Ser}, not null
   * @serialData <pre>
   *  out.writeByte(5);        // identifies a JapaneseEra
   *  out.writeInt(getValue());
   * </pre>
   */
  private Object writeReplace() {
    return new Ser(Ser.JAPANESE_ERA_TYPE, this);
  }

  void writeExternal(DataOutput out) throws IOException {
    out.writeByte(this.getValue());
  }

  static JapaneseEra readExternal(DataInput in) throws IOException {
    byte eraValue = in.readByte();
    return JapaneseEra.of(eraValue);
  }

}
